Exhaust gas catalyst for internal combustion engines

Abstract

An exhaust gas catalyst includes: catalyst particles that clean exhaust gas; and magnetic particles that are placed around the catalyst particles and that generate heat upon absorption of microwaves. Each of the magnetic particles includes: a core portion composed of a ferromagnetic material capable of generating heat upon absorption of microwaves; and a shell portion coating a surface of the core portion, the shell portion having a property of permitting passage of microwaves, the shell portion being superior to γ-alumina or θ-alumina in a property of blocking gases.

What is claimed is: 
     
         1 . An exhaust gas catalyst for an internal combustion engine, comprising:
 catalyst particles that clean exhaust gas of the internal combustion engine; and   magnetic particles that are placed around the catalyst particles and that generate heat upon absorption of microwaves, wherein each of the magnetic particles includes:   a core portion composed of a ferromagnetic material capable of generating heat upon absorption of microwaves; and   a shell portion coating a surface of the core portion, the shell portion having a property of permitting passage of microwaves, the shell portion being superior to γ-alumina or θ-alumina in a property of blocking gases.   
     
     
         2 . The exhaust gas catalyst according to  claim 1 , wherein the shell portion is composed of at least one material of: i) silicon nitride; ii) aluminum nitride; iii) manganese oxide; iv) α-alumina; and v) silica. 
     
     
         3 . The exhaust gas catalyst according to  claim 1 , wherein the shell portion is composed of at least one material of: i) α-alumina; and ii) silica. 
     
     
         4 . The exhaust gas catalyst according to  claim 1 , wherein a BET specific surface area of the shell portion is less than 180 m 2 /g. 
     
     
         5 . The exhaust gas catalyst according to  claim 1 , wherein a BET specific surface area of the shell portion is less than 105 m 2 /g. 
     
     
         6 . The exhaust gas catalyst according to  claim 1 , wherein a pore volume of the shell portion is less than 0.7 cm 2 /g. 
     
     
         7 . The exhaust gas catalyst according to  claim 1 , wherein a pore volume of the shell portion is less than 0.6 cm 2 /g. 
     
     
         8 . The exhaust gas catalyst according to  claim 1 , wherein the ferromagnetic material includes at least one material of: i) ferromagnetic oxide; ii) a ferromagnetic metal; and iii) a hexagonal ferrite. 
     
     
         9 . The exhaust gas catalyst according to  claim 1 , wherein the catalyst particles include at least one material of: i) γ-alumina; ii) θ-alumina; and iii) zirconia.